Fig. 5: Topographic anisotropy in perceived spatial extents.
Across 27 observers, each represented by a single dot, the radial bias indice of perceptual anisotropy in the radial orientation condition, \({{RI}}_{{{{{{\rm{perc}}}}}}}(\theta ={{{{{\rm{radial}}}}}})\), is plotted against that in the tangential orientation condition, \({{RI}}_{{{{{{\rm{perc}}}}}}}(\theta ={{{{{\rm{tangential}}}}}})\). The histograms at the bottom and on the right show the across-individual distributions of \({{RI}}_{{{{{{\rm{perc}}}}}}}\) values in the radial and tangential orientation conditions, respectively. Note that most of the \({{RI}}_{{{{{{\rm{perc}}}}}}}\) values fall on the positive side in the radial orientation condition and on the negative side in the tangential condition, which indicates that the anisotropy of perceived spatial extents is co-axially biased. Given this co-axial bias, the RIpercs were converted into the co-axial bias indices (CIpercs) by keeping their signs in the radial orientation condition (\({{CI}}_{{{{{{\rm{perc;}}}}}}\theta ={{{{{\rm{radial}}}}}}}\) = \({{RI}}_{{{{{{\rm{perc;}}}}}}\theta ={{{{{\rm{radial}}}}}}}\)) while flipping them in the tangential condition (\({{CI}}_{{{{{{\rm{perc;}}}}}}\theta ={{{{{\rm{tangential}}}}}}}\) = \(-1\times{RI}_{{{{{{\rm{perc;}}}}}}\theta ={{{{{\rm{tangential}}}}}}}\)) (read the main text for the rationale). The histogram in the upper-left corner shows the across-individual distribution of the differences in \({{CI}}_{{{{{{\rm{perc}}}}}}}\) between the two orientation conditions, \({{CI}}_{{{{{{\rm{perc;}}}}}}\theta ={{{{{\rm{radial}}}}}}}-{{CI}}_{{{{{{\rm{perc;}}}}}}\theta ={{{{{\rm{tangential}}}}}}}\). Dots, 27 observers; Black crosshairs, across-individual means, and their standard errors.
